Texture evolution and corrosion behaviour of Sn–1.5 wt% Cr coatings containing Graphene oxide

Abstract

ABSTRACT Sn–1.5 wt% Cr coating incorporated with varying quantity of Graphene oxide (GO) were deposited using electrodeposition technique on mild steel strip using aqueous electrolyte bath. The aqueous bath was dispersed with GO with increasing concentrations in mg/L (31.2, 62.5, 93.7, 125 and 156.2). All the coatings exhibited compact morphology and contained Sn and Cr-oxide phases (CrO2 and Cr2O3). Potentiodynamic polarisation and impedance spectroscopy techniques showed that the coating corrosion resistance increased for the initial addition of GO till Sn–Cr–GO2 coating (from 62.5 mg/L of GO) and it decreased thereafter for higher GO additions. The corrosion current density value exhibited by pristine Sn–Cr, Sn–Cr–GO2 and Sn–Cr–GO5 (from 156.2 mg/L of GO) was 1.38, 0.5 and 4.09 µA/cm2, respectively. Characterisation of the coating texture showed that between all the coatings, low angle grain boundary fraction was highest for Sn–Cr–GO2 coatings. The highest corrosion resistance was on account of special impermeable and inert properties of GO which was uniformly distributed in the coating matrix and the presence of a large fraction of low energy low angle grain boundaries. High corrosion rate in the case of Sn–Cr–GO5 coatings was attributed to the agglomeration of GO in the coating matrix which resulted in non-uniform coating morphology with high surface defects.